/*
 * Copyright 2002-2018 the original author or authors.
 *
 * Licensed under the Apache License, Version 2.0 (the "License");
 * you may not use this file except in compliance with the License.
 * You may obtain a copy of the License at
 *
 *      https://www.apache.org/licenses/LICENSE-2.0
 *
 * Unless required by applicable law or agreed to in writing, software
 * distributed under the License is distributed on an "AS IS" BASIS,
 * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
 * See the License for the specific language governing permissions and
 * limitations under the License.
 */

package org.springframework.web.servlet.mvc.method.annotation;

import org.springframework.core.MethodParameter;
import org.springframework.lang.Nullable;
import org.springframework.web.bind.support.WebDataBinderFactory;
import org.springframework.web.context.request.NativeWebRequest;
import org.springframework.web.method.support.HandlerMethodArgumentResolver;
import org.springframework.web.method.support.ModelAndViewContainer;

import javax.servlet.ServletResponse;
import java.io.IOException;
import java.io.OutputStream;
import java.io.Writer;

/**
 * Resolves servlet backed response-related method arguments. Supports values of the
 * following types:
 * <ul>
 * <li>{@link ServletResponse}
 * <li>{@link OutputStream}
 * <li>{@link Writer}
 * </ul>
 *
 * @author Arjen Poutsma
 * @author Rossen Stoyanchev
 * @author Juergen Hoeller
 * @since 3.1
 */
public class ServletResponseMethodArgumentResolver implements HandlerMethodArgumentResolver {

    @Override
    public boolean supportsParameter(MethodParameter parameter) {
        Class<?> paramType = parameter.getParameterType();
        return (ServletResponse.class.isAssignableFrom(paramType) ||
                OutputStream.class.isAssignableFrom(paramType) ||
                Writer.class.isAssignableFrom(paramType));
    }

    /**
     * Set {@link ModelAndViewContainer#setRequestHandled(boolean)} to
     * {@code false} to indicate that the method signature provides access
     * to the response. If subsequently the underlying method returns
     * {@code null}, the request is considered directly handled.
     */
    @Override
    public Object resolveArgument(MethodParameter parameter, @Nullable ModelAndViewContainer mavContainer,
                                  NativeWebRequest webRequest, @Nullable WebDataBinderFactory binderFactory) throws Exception {

        if (mavContainer != null) {
            mavContainer.setRequestHandled(true);
        }

        Class<?> paramType = parameter.getParameterType();

        // ServletResponse, HttpServletResponse
        if (ServletResponse.class.isAssignableFrom(paramType)) {
            return resolveNativeResponse(webRequest, paramType);
        }

        // ServletResponse required for all further argument types
        return resolveArgument(paramType, resolveNativeResponse(webRequest, ServletResponse.class));
    }

    private <T> T resolveNativeResponse(NativeWebRequest webRequest, Class<T> requiredType) {
        T nativeResponse = webRequest.getNativeResponse(requiredType);
        if (nativeResponse == null) {
            throw new IllegalStateException(
                    "Current response is not of type [" + requiredType.getName() + "]: " + webRequest);
        }
        return nativeResponse;
    }

    private Object resolveArgument(Class<?> paramType, ServletResponse response) throws IOException {
        if (OutputStream.class.isAssignableFrom(paramType)) {
            return response.getOutputStream();
        }
        else if (Writer.class.isAssignableFrom(paramType)) {
            return response.getWriter();
        }

        // Should never happen...
        throw new UnsupportedOperationException("Unknown parameter type: " + paramType);
    }

}
